Hearing aids receive and amplify sounds and provide the amplified sounds to hard-of-hearing persons. In general, the hearing aids are classified according to amplification methods, circuit characteristics, and shapes.
According to amplification methods, the hearing aids are classified into a linear amplification type by which sounds are linearly amplified and a non-linear amplification type by which sounds are non-linearly amplified. According to circuit characteristics, the hearing aids are classified into an analog type implemented by analog circuits, and a digital type implemented by digital circuits. However, the typical hearing aids are classified according to shapes of the hearing aids.
According to shapes of the hearing aids, the hearing aids are classified into pocket type or box type hearing aids, BTE (Behind-The-Ear) type hearing aids, ITE (In-The-Ear) type hearing aids, ITC (In-The-Canal) type hearing aids, CIC (Completely-In-the-Canal) type hearing aids, and eyeglass type hearing aids.
The hearing aids are developed in various ways according to convenience of users or depending on the intended use. Hearing aids are currently under development in various types.
In order to increase performance and functionality of hearing aids, various us additional devices are recently added to the hearing aids. As well, the number of components such as microphones is changed in various ways. One of techniques to increase performance of hearing aids is a technology of strengthening directivity for a specific direction, to thereby make sound sources that are generated in a particular direction better heard than those occurring in another direction.
FIG. 1 is a block diagram showing a conventional hearing aid to obtain a directional pattern.
FIG. 1 shows a hearing aid that is disclosed in Korean Patent Laid-open Publication No. 2009-0045453 published on May 8, 2009, and that includes two microphones M1 and M2, a time delay ID, an adder ADD, and a signal processor PCS. The two microphones M1 and M2 receive ambient sounds, respectively, to then generate a sound signal. The time delay D delays the sound signal generated the microphone M2 by a predetermined time and outputs the time-delayed sound signal. The adder ADD adds the sound signal output from the microphone M1 and the output signal of the time delay D, and outputs the added result. The signal processor PCS performs signal processing such as amplification or noise cancellation with the output signal of the adder ADD, to then output the sound via a speaker (not shown). Accordingly, the pattern of the directivity of the hearing aid is kept constant. For example, sounds occurring in front of users can be heard well than sounds occurring in the other directions.
However, the conventional hearing aid shown in FIG. 1 has a drawback that a direction orienting sound sources is fixed to a particular direction, to thus cause inconveniences of controlling delay time in each case in order to change the direction of orientation of the hearing aid.